1. Field of the Invention
The present invention relates to an electronic component mounting machine and method therefor, and more particularly to an electronic component mounting machine and method therefor in which the components are fed sequentially from an electronic component storage section, picked up by pick-up nozzles, and mounted onto predetermined positions on printed circuit boards.
2. Description of the Related Art
In electronic component mounting machines, electronic components are generally supplied one at a time from a reel having a paper or plastic tape containing the electronic components to a component feeder, then the components are picked up by a head unit, and then the components are mounted onto a printed circuit board. The head unit is generally moved in XY directions on a plane parallel to the circuit board by means of an XY robot. One example is shown in FIG. 10.
Referring to FIG. 11, the head unit 4 has generally one or more component pick-up units 7, and is supported on the XY robot 6 via a mechanical interface member 8. The component pick-up unit 7 has a structural member 9 fixed on the surface of the interface member 8, a bracket 11 movable up and down along a vertical straight guide 10 supported on the structural member 9, a z-motor 13 for driving the bracket 11 in up-and-down direction via a ball screw 12 mounted on the bracket 11, a pick-up nozzle 15 attached at the lower end of a vertical shaft 14 mounted on the bracket 11, a .theta.-motor 16 mounted on the bracket 11 for controlling the angular position of the pick-up nozzle 15 by rotating the shaft 14 about its axis, a position detector 18 mounted on the structural member 9 for detecting the position of an electronic component picked up by the pick-up nozzle 15, and a camera 19 mounted on the structural member 9 for recognizing marks on the circuit board 5, the pick-up position on the component 17 at the time of picking up the component 17, and the position of the component 17 mounted on the circuit board 5.
By matching the distance between the pick-up nozzles 15 on the pick-up units 7 with the distance between the top ends of the feeders 3, a plurality of pick-up units 7 can pick up a plurality of components 17 simultaneously, and the same number of picked up components 17 as the number of pick-up nozzles 15 can be placed on the board 5 simultaneously at each XY movement by the XY robot 6, and hence the mounting time of the components 17 can be shortened.
In one configuration, a component mounting machine having an X guide rail on which two head units are mounted independently movable to each other is disclosed, where the components picked up by both heads are placed onto respective predetermined positions on two boards independently positioned from each other. As the number of pick-up units increases with respect to the XY robot, the cycle time of picking up and mounting the components is theoretically reduced, which improves productivity. A problem with this method is that productivity might be reduced relative to the increase of the number of pick-up units because the increase in number of pick-up units necessarily increases the transportation mass for the XY robot, and it may become difficult to maintain the moving speed and acceleration of the units, which sometimes results in longer cycle time of picking up and mounting the components.
In another configuration, a component mounting machine has a head unit that is moved only in an X direction (transporting direction of the board) and the board is moved in a Y direction perpendicularly thereto is disclosed. A problem with this configuration is that the machine occupies a large installation area and has difficulty in attaining high speed operation.
In still another configuration the component mounting machine comprises two beams in the X direction, each having a head unit mounted thereon is disclosed. A problem with this configuration is that component storage sections have to be provided in front and rear sides of the machine, which means a complicated structure, higher cost for a production line, and higher cost of the machine.
In still another configuration, a component mounting machine comprising an X rail having two head units is disclosed. A problem with this configuration is that after mounting a component on one side of a board, the X rail has to be moved in a Y direction, and then the other component may be mounted onto the other side of the board. Therefore, the mounting cycle time is longer.
Thus, as demonstrated by the foregoing problems, there exists a need for an electronic component mounting machine and method therefor for mounting electronic components at high speed without increasing installation area of the machine and its cost with a simple structure.